Electric heating element.



S. L. KELLY.

ELECTRIC HEATING ELEMENT.

APPLICATION FILED 0012s, 1916.

Patented J an. 15, 1918.

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ELECTRIC E-IEATIHG ELEMENT.

Specification of Letters Patent.

Patented Jan, as, rare.

Application filed Uctobcr 23, 1916. Serial No. 127,167.

To all whom it may concern:

Be it known that I, 'SHERMAN L. KELLY, a citizen of the United States, and a resident of Toledo, 1n the county of Lucas and State of Ohio, have invented a certain new and useful Electric Heating Element; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanyin drawings, and to the characters of re erence marked thereon, which form a part of this specification.

This invent1on relates to electric heating units and particularly to those of the open air heating type for use in ovens of electric stoves.

The object of my invention is the provision of an improved element of this type which is simple,strong, cheap and durable in its construction, and highly eificient in use.

A further object of my invention is the provision of improved terminal connecting means whereby the terminals are not only protected more orless from the heat enerated by the element but are prcventeo from oxidizing and setting'up a resistance which in itself causes heat and results in injury to the terminal.

The invention is fully described in the following specification, and While, in its broader aspect it is capable of embodiment in numerous forms, a preferred embodiment thereof is illustrated in the accompanying drawings, in which,

Figure 1 is a b6ttom perspective view of a heating element embodying my invention. Fig. 2 is an enlarged fragmentary end ele vation thereof with a terminal post in engagement with an electric connecting socket, the socket being in central longitudinal section. Fi 3 is an enlarged perspective view of one o the insulating blocks of the element. F ig. 4 is an enlarged perspective view of one of the clips employed to assist in retaining the parts of the element assembled, and Fig. 5 is a diagram of element wiring.

Referring to the drawings, 1 and 2 designate the top and bottom members, respectively, of an element embodying the invention, each of which comprises a rectangular frame 3 preferably of heavy wire, cross bars 4 extending in one direction and-cross bars 5 extending in the other direction across the the frame and fixed thereto at their ends, as by electric welding. lhe bars 5, in the present instance, extend across the outer sides of the respective bars 4 and the ends of the bars *4: preferably lap the outer sides of the respective frames The bars 4, for the greater portion of their lengths, are inwardly ofiset from their ends or counterr sunk with respect to the frame sides to permit them to lie in the plane of said sides. The bars a and 5011 the top and bottom members'are arranged in respective opposed relation, except that the top member preferably has a greater number of cross-bars 5 than the bottom member.

A plurality Oinarrow insulatingblocks 6 are placed end to end between the sets of opposed crossbars 4: and form a plurality of transversely spaced insulating walls 6, which extend from end to end of the element. These blocks have their top and bottom edges longitudinally grooved to permit the bars 4 to seat therein, and each has one or more apertures 7 therethrough for receiving the heating coils. Short insulating blocks 8 abut at their inner ends against the outer insulating walls 6 transversely thereof, and are disposed between opposed crossbars 5, which seat in respective edge grooves thereof, as shown. lit is thus evident that the bars a and Eiserve to maintain therespective insulating blocks 6 and 8 inposition between. the top and bottom members of the element. Each of the blocks 8. is provided at its inner end with a notch or aperture 9 and at its outer end with a notch or aperture 10. The insulating blocks 6 and 8 are intended to carry the heating coils or resistance conductors of the element and also their terminal posts, as hereinafter described.

The insulatin properly assent led between the top and bottom members, the separate parts are clamped in such position by corner clamps each of which comprises a pair of plates 11 blocks 6 and 8 having been for. embracing the outer sides of the op-- posed frames 2 and 3 at a corner thereof, a bolt 12 for drawing the plates 11 into'cooperating clamping engagement with the llll ends longitudinally notched or recessed to provide spaced fingers 15, which straddle the respective bars 4 andbend over or around a registering cross-bar 5, as shown.

The element, in the present instance, contains two separate resistance conductors or heating coils, one of which is designated 16 and extends trom a terminal post 17 to a similar post 18, while the other is designated 19 and extends from a terminal. post 20 to the post 18. The posts 17, 18 and 20, for the purpose of rigidity, are carried by and rigidly project from the blocks 6 of two separate ro'ws, as shown. The coils 16 and 19 thread backward and forward through registering apertures 7 in the spaced insulating walls 6 and have their overlapped portions at the outer sides of the outer Walls 6 extending through the notches 9 and 10 therein, in a manner to maintain the loops of the different coils spaced as shown. For instance, the coil 16, after leaving the post 17 extends through registering apertures '2' in the walls 6, thence loops around a block 8 in the outer notch 10 thereof, and backward through a set of registering apertures in the walls 6*, thence loopsthrough the inner notch 9 of the block 8, and so on backward and forward through the walls 6 to the post 18. The coil 19 has its first loop within the first loop of the coil 16 and so passes through the inner notch 9 of the first block 8 in order, and has its second loop without the second loop of the coil 16 and so passes'through the outer notch 10 of the next block 8 in order, and so on through the rest of the course.

Each post 17, 18 and 20 is intended to removably fit into a respective contact socket 21, which is fixedly carried by the stove or apparatus in which the heating element is to be used. Each socket comprises an insulating block 22 of elongated form with a hole or socket 28 in its outer end in which a pair of spaced contact fingers 24 of spring form are disposed, and which cooperate to form a socket for receiving the retpective terminal post of the element, the fin ers being forced apart when the post is inseritfed therebetween. The opposite or inner end of the socket block 22 is provided therein with an opening 2 of considerable length and communicating at its inner end with the socket 23 in longitudinal register with the socket formed by the contact fingers 24 so that the terminal post can be inserted through the opening 25 and into the space between said fingers, as shown. It is therefore necessary to have the terminal posts of considerable length. While the opening 25 is large at its outer end to facilitate the insertion of a post therein, it is restricted at its inner end'to-substantially the size of the post to reduce to a minimum the amount of heat which will pass therethrough to the oint of contact of the post In practice, electrical contacting surfaces,

when heated, become oxidized, and in conse,

quence set up a resistance which itseii causes heating and injuriously afiec'm the contact,

In order to prevent this it have not only remotely placed the post contact sockets with respect to the element to prevent a high heating of such contacts by heat generated by the element, but I make both the terminal posts and contact fingers 2d of a metal which, while a good electrical conductor, is a poor heat conductor, thereby keeping the terminal. contacts substantially cool. For this purpose I preferably employ ldonel metal, which is 85% nickel and 15% copper. It is found that this, in conjunction with the positioning of the contact at a considerable distance from the heating element, is very effective in maintaining the contacts cool and very materially prolongs the life of the contacts by preventing oxidation,

The purpose of providing the bottom member of the element with less cross-bars 5 than the top member is to lessen the liability of a heating coil having contact with the sub acent cross-bar by reason of the coil sagging at any point therein.

It is apparent that I have provided a heating element which is simple, cheap and durable in its construction, capable of having the parts thereof easily and quickly assembled, and which has its contacts so ar ranged and constructed as to reduce to a minimum the liability of heat oxidation.

I wish it understood that my invention is not limited to any specific construction, arrangement or form of the parts except in so far as such limitations are specified in the claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is-- i 1. In a heating element, top and bottom members of grate form separably connected together, insulating block's disposed between said members and held in assembled position thereby, and resistance conducterscarried by said blocks;

2. An electric heating element having spaced separably connected top and bottom members, each havingcross bars running in dilterent directions thereon, insulating blocks disposed between said members and held in position thereby, said blocks having edge grooves receiving portions of said'ba'rs, and resistance conductors carried by said blocks.

3. An electric heating element having spaced top andloottom members separably connected together, each of said members having a rectangular frame and cross bars extending in opposite. directions across the same and fixed to the frame, insulating blocks disposed between said frames and.

held in position by engagement with certain of said bars, means for securing the top and bottom members together, and resistance conductors carried by said blocks between said members.

4. An electric heating element having spaced top and bottom members, each comprising a frame and separate sets of cross bars connecting opposite sides of the frame, one set crossing the other, a set of insulating blocks disposed between said members and forming transversely spaced insulating walls, which walls removably interengage with opposed bars of one set on the two members and are held in assembled position disposed transversely of said insulating walls and at the outer side of the outer of said walls, said second set of blocks interengaging with and being held in position by opposed cross bars of the other set of cross bars of said members, means for securing the top and bottom members in assembled block-holding position, and resistance conductors extending backward and forward through said insulating blocks and carried thereby.

In testimony whereof I have hereunto signed my name to this specification.

SHERMAN L. KELLY. 

